Setting a system-wide default branch name
The default branch for a repository is its integration branch for work. In pull request workflows, its where feature branches are targeted. It's also the first branch created in a new repository.
As a Bitbucket Data Center administrator, you can select how this branch is named by going to 
> Default branch name. On this page your options are:
| Option | Description |
|---|---|
| Use the Git default name | The name given to the default branch is based on the installed Git version:
|
| Set a custom default name | You can set an set an instance-wide custom default name for this branch. This custom name will be used instead of the Git name, and when a user creates a new repository they’ll see it prefilled in the default branch name field. They can then use this name, or enter a branch name of their own. |
When creating a new repository, users can leave the Default branch name field empty. If they do, the name given to the default branch will be the default branch name that has been configured for the instance.